An instrument panel in a vehicle has many operating switches which include the control switches for the operating air conditioning system, the audio system and the car navigation system.
The number of the switches has increased in recent years, due to the development of information technology in vehicles and a growing need for driving support systems. Due to the increase in the number of the switches, it has been difficult to locate all the switches on the instrument panel. Therefore a display device, such as a liquid crystal display device, has been used as an operation panel to display switches or operation items on a screen, as shown in FIG. 4 of Japanese unexamined patent publication No.2002-120545.
The display device can display a screen having the operation items for controlling the system corresponding to any of the systems. However, if there are many operation items for one system, all of the items cannot be displayed on a single screen. The display device must have hierarchically structured screens for the systems, e.g. the air conditioning system, the audio system or the navigation system. Accordingly when one of the operation items is placed in a lower-level screen, a user must move sequentially from the top screen to a lower-level screen to operate the item. If the item is frequently used, the use of the items is complicated for the user.